Stock-Based Compensation

6 Months Ended

Jun. 30, 2014

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Stock-Based Compensation

(12) Stock-Based Compensation

The Company recognizes all share-based payments to employees and directors as expense in the statements of operations and comprehensive loss based on their fair values. The Company records compensation expense over an award’s requisite service period, or vesting period, based on the award’s fair value at the date of grant. The Company’s policy is to charge the fair value of stock options as an expense, adjusted for forfeitures, on a straight-line basis over the vesting period, which is generally four years for employees and three years for directors.

The Company recorded charges of $785,000 and $265,000 in its statements of operations and comprehensive loss for the three months ended June 30, 2014 and 2013, respectively, and $1,320,000 and $518,000 in its statements of operations and comprehensive loss for the six months ended June 30, 2014 and 2013, respectively, for stock-based compensation expense attributable to share-based payments made to employees and directors. The fair value of each option award is estimated on the date of grant using the Black-Scholes option-pricing model. The following assumptions apply to the options to purchase 2,116,000 and 1,720,083 shares of common stock granted to employees and directors during the six months ended June 30, 2014 and 2013, respectively:

	Six Months Ended June 30,
	2014			2013
Average risk free interest rate		1.6	%		0.9	%
Expected dividend yield		—			—
Expected lives (years)		4.8			5.0
Expected volatility		83.0	%		61.0	%
Weighted average grant date fair value of options granted during the period (per share)	$	2.61		$	0.36
Weighted average exercise price of options granted during the period (per share)	$	4.01		$	0.69

The expected lives and the expected volatility of the options granted during the six months ended June 30, 2014 and 2013 are based on historical experience. All options granted during the six months ended June 30, 2014 and 2013 were granted at exercise prices equal to the fair market value of the common stock on the dates of grant.